linux-kernel - Re: [PATCH v11] NVMe: Convert to blk-mq

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Date:	Fri, 15 Aug 2014 12:09:47 +0200
From:	Matias Bjorling <m@...rling.me>
To:	Keith Busch <keith.busch@...el.com>, Jens Axboe <axboe@...com>
CC:	Matthew Wilcox <willy@...ux.intel.com>,
	"Sam Bradshaw (sbradshaw)" <sbradshaw@...ron.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-nvme <linux-nvme@...ts.infradead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Rob Nelson <rlnelson@...gle.com>,
	Ming Lei <tom.leiming@...il.com>
Subject: Re: [PATCH v11] NVMe: Convert to blk-mq

On 08/15/2014 01:09 AM, Keith Busch wrote:
>
> The allocation and freeing of blk-mq parts seems a bit asymmetrical
> to me. The 'tags' belong to the tagset, but any request_queue using
> that tagset may free the tags. I looked to separate the tag allocation
> concerns, but that's more time than I have, so this is my quick-fix
> driver patch, forcing tag access through the hw_ctx.
>

I moved nvmeq->hctx->tags into nvmeq->tags in the last version. I missed 
the free's in blk_mq_map_swqueue. Good catch.

The previous method might have another problem. If there's two 
namespaces, sharing tag set. The hctx_init fn could be called with 
different hctx for an nvmeq, leading to false tag sharing between nvme 
queues.

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